In August 1924, the long-suffering Stanislaus Joyce sent a letter of complaint to his brother, James, in which he mentioned his difficulties with Ulysses. "The greater part of it I like," he wrote, before adding with characteristic bluntness: "I have no humour with episodes which are deliberately farcical... and as episodes grow longer and longer and you try to tell every damn thing you know about anybody that appears or anything that crops up, my patience oozes out."

In his exasperation, Stanislaus anticipated the fate that awaited Ulysses, a novel that, almost 90 years after its publication, seems to have utterly exhausted the patience of the ordinary reader to the point where it is now perhaps the most unread literary masterpiece of all time. Declan Kiberd begins Ulysses and Us, his inspired reclamation of Joyce's great epic of the everyday, by acknowledging the great irony that "a book which set out to celebrate the common man and woman" has "endured the sad fate of never being read by many of them".

Kiberd's previous books include the brilliant Inventing Ireland: the Literature of the Modern Nation and Ulysses: Annotated Students' Edition. The preoccupations of both books come together in Ulysses and Us. The first - and more interesting - part of the book is a polemic, which tackles what Kiberd sees as the enduring misrepresentation of Joyce's dauntingly ambitious novel: "How can a book like Ulysses have been so misread and misunderstood?" he asks early on. "How was it taken as a product of a specialist bohemia against which it was in fact in open revolt? Why has it been called unreadable by the ordinary people for which it was intended?" In the second part of Ulysses and Us, Kiberd goes on to give a chapter by chapter breakdown of the novel, best read alongside the original text, to help, it would seem, those "ordinary people" reclaim the book.

If Kiberd tends to downplay the novel's difficulty, he is a tireless and refreshingly clear-headed champion of its myriad rewards. Even if you do not have the patience to read Ulysses with Kiberd's chapter-by-chapter guide nearby, you should try and read his two opening chapters, entitled "How Ulysses Didn't Change the World" and "How it Might Still Do So". Together, they make up a rigorous, politically combative and heartfelt argument for the continuing relevance of a novel "that has much to teach us about the world - advice on how to cope with grief; how to be frank about death in the age of its denial; how women have their own sexual desires and so also do men; how to walk and think at the same time... how to tell a joke and how not to tell a joke..."

It is his contention that Ulysses has suffered most at the hands of its so-called champions, the seemingly endless stream of academics that constitutes the Joyce industry in all its self-sustaining, self-defeating specialisation. Their cardinal sin, he insists, is not their wilful obfuscation or often surreal jargon - "parallax, indeterminacy, consciousness-time" - but their determination to wrest the book from its actual - and symbolic - setting.

"Many of them reject the notion of a national culture, assuming that to be cultured nowadays is to be international, even global, in consciousness," writes Kiberd. "In doing this, they have removed Joyce from the Irish context which gave his work so much of its meaning and value."

As Kiberd points out, Ulysses is a novel so rooted in a sense of place that, as its author once memorably put it, if Dublin was to "suddenly disappear from the Earth it could be reconstructed out of my book". (Joyce was so obsessive in his devotion to detailing the city he had fled that he once wrote to his Aunt Josephine in Dublin asking: "Is it possible for an ordinary person to climb over the railings of No 7 Eccles Street either from the path or the steps, lower himself from the lowest part of the railings till his feet are within two feet or three off the ground and drop unhurt?")

Ulysses is a novel that, long before the term was invented, attempted to map out the psychogeography of Joyce's native city. It is also, though, as Kiberd reminds us, a novel "written to celebrate ordinary people's daily rounds". Unlike Flaubert, say, Joyce had no interest in writing fiction with an underlying social message. Instead, he evoked, through the wanderings and musings of his Jewish Everyman, Leopold Bloom, the latent sense of wonder that often underpins the everyday.

It is also a book about the passing on of wisdom from one generation to another, from one remarkably content older Dubliner, Bloom, to the younger, altogether more troubled Stephen Dedalus. Kiberd's subtitle is "The Art of Everyday Living" and that is what he emphasises throughout.

For all that, though, Ulysses does remain a difficult read and, I suspect, seldom finds its way on to book club reading lists. More worryingly, as Kiberd points out, it has also fallen off the syllabuses of many university degree courses in English literature. Students no longer arrive at college with a thorough grounding in the Latin and Greek classics. "What has been lost," writes Kiberd, "is a sense of chronology, an understanding of the evolution of English literature on which so much of the meaning of the text depends."

What has also been lost is the notion of the novel as a medium for self-improvement, a notion Joyce believed in wholeheartedly. He insisted, as Kiberd succinctly puts it, "on the use-value of art" and saw Ulysses as a book that could engage both scholars and ordinary readers alike. This now seems like wishful thinking, but, as Kiberd states: "Ulysses took shape in a world which had known for the first time the possibilities of mass literacy and the emergence of working men's reading libraries." That utopian ideal now seems distant .

The last word, though, should not, for once, go to Joyce but to the common reader, in this instance Declan Kiberd's father, a Dubliner through and through. "My father loved Ulysses as the fullest account ever given of the city in which he lived," writes Kiberd. "There were parts that baffled or bored him, and these he skipped, much as today we fast-forward over the duller tracks on beloved music albums. But there were entire passages he knew almost by heart."

That is Ulysses as I know it and love it: a novel that can be read in fragments, dipped into and out of, digested in small, rich, satisfying chunks. A novel, in fact, for our time.

Ulysses, a brief history: The story behind the book

Begun in 1914, when James Joyce was 32 and living in Paris, Ulysses was first serialised in the American journal, The Little Review, while it was still being written. When the review printed a scene of masturbation, it faced a prosecution for obscenity, which it lost.

The finished book was first published in Paris by Shakespeare and Company in 1922. It printed only 1,000 copies and when Random House tried to import some of these to the US, the books were seized by customs.

This first edition was found to have between 2,000 and 5,000 textual errors - although, as the book is made up of 264,834 words (using a vocabulary of 30,030 words), and almost a third of it was written in the margins of the manuscript, none of the 11 editions since 1922 has provided a perfect text either. Most English editions follow the revised edition published by Bodley Head in 1960.

Ulysses is split into 18 chapters, or "episodes", all of which take place on the same day: 16 June 1904. It was been filmed twice, adapted for the stage and broadcast in dramatised form on the radio.

Despite Ulysses generally being regarded as a difficult read, Dublin and Joyce aficionados elsewhere celebrate it annually with Bloomsday on 16 June, enjoyed by thousands of people, many of whom will never have read it. The book was set on this date because it marked Joyce's first real date with his future wife, Nora. Bloomsday involves readings, pub crawls, and other festivities; in Spokane, Washington, there is a charity event called the Bloomsday run (in fact held on the first weekend in May).